Granular carbon and process of making the same



' I 1,646,389 1927' 5., N. BUNTING I GRANULAR CARBON AND PROCESS OF MAKING THE SAME Filed April 29. 1925 INVENTO/g. [7/774/ 4 6/4975 50/25) BY M16 ATTOR EYS.

Patented Oct. 1927.

UNITED. STATES {PATENT OFFICE.

IELIMIIER NEWMAN BUNTING, ,OF EAST ORANGE, NEW JERSEY.

GRANULAR CARBON AND PROCESS OF MAKING THE SAME.

Application filed Apri1'29, 1925. Serial No.' 26,696.

' i The object of the invention is to produce element of microphone transmitters occa-' sions undue hissing or burning, that 1t is- .not as sensitive as might be desired, and, moreover, that its resistance so increases with use that the usability of the transmitters may be greatly impaired.

The present invention overcomes the disadvantageslspecified, and others, and results in a granular carbon which is highly efficient forits intended purpose in that, inter alia, it minimizes hissing, is highly sensitive, electrically, and maintains the desired resist ance without material impairment by even long use.

Speaking generally, the invention, in its preferredform, embodies a process wherein suitable carbonaceous material, such'as coal, cocoanut shells, etc., in a ground condition, is subjected to a preliminary heating or preliminary roast at agradually increasing temperature and for a somewhat protracted. period, in the presence of a nonoxidizing, i. e., reducing atmosphere. The resulting material is heated, preferably at a higher temperature, either in a non-oxidizing at mosphere, or one containing a comparatively small quantity of an oxidizing gas or gases, such asair in limited quantity. However, I prefer, when the two operations specified are employed, to use a non-oxidizing atmosphere in both instances.

The accompanying drawing shows, more or less, diagrammatically, one form of apparatus which I have found useful in practicing the invention, though other types or forms of apparatus which may be used will' readily suggest themselves to those skilled in the art.

Figure 1 is a longitudinal medial section of that portion of the apparatus wherein the pig-treatment adverted to is carried out; an

Figure 2 is that portion of the apparatus, partly in longitudinal section and partly in elevation. wherein the second and final treatment of the material is completed.

Referring to Figure 1 of the drawings, A

is an electrical heating element or unitof a commonly employed construction embodying an electrical heating element or coil B encased between two insulating tubes or jackets c, 0, respectively, of suitable material, such as a vitrified refractory tube. C is theretort or chamber which may be of cylindrical form in which the carbonaceous material is first heated, the inlet end of which retort is provided with a metallic cap or head D, screwed thereon, having a gaseous inlet E, and. the outlet end of said tube is provided with a cap or closure F, having a gaseous outlet G. The material to be treated is preferably confined in crucibles H, positioned within retort C, which crucibles may be readily introduced into or withdrawn from said retort by unscrewing closure D. j

The material having been subjected to the pre-roast, to be described with more particularity hereinafter, is then introduced, see Figure 2, into a hopper I, preferably of glass,

having a joint connection z, through which the material isfed to a rotary inclined heating retort or heater J, preferably cylindrical, and provided with an electrical heating ele ment,1 similar to that previously described, embodying a heating coil B encased between insulatinglmembers or cylinders d, d, re-

spectively. Cylindrical retort J may be rotated in any suitable way, as by a suitable pinion e mounted on the cylinder.

The inlet end of retort J is provided with arotatable feedingielement 7, adapted to be rotated through a gear or pulley, shown diagrammatically at g. The feed inlet of tube J is also provided with a gas inlet tube It. Cylinder J is preferably provided with two mercury seals indicated at 2", 6 respectively, whereby the inlet end of the cylinder is rendered gas tight. Cylinder J may be mounted for rotation in bearings j, 7", which it will be understood, are provided with paratus and, its general manner of operation,

the following specific description of appli cants process Will be readily understood- The carbonaceous material to be treated. is placed in crucibles Whichare then introduced into cylinder C, and heated therein at a minimum of 500 degrees C., though the ma-- terial may be allowed to attain a temperature of say from 900 degrees to- 1000 degrees C1,

or even, higher. The maximum temperature havingbeen reached, the heatin is continued at such temperature fora period of approximately 5 hours. The heating of the material as described is conducted in a non-oxidizing atmosphere, such as that of hydrogen or nitrogen, preferably the former, which may be introduced intoretort '6- through gas inlet/E.

The thus treated material, the heating' ot Whichmay be termed pro-heating or preroasting, is'introduced, into hopper I from which it is fed, as hereto-foredescribed, into retort or heater J. In retort J the material is so thoroughly agitated and mixed that all the particles are thoroughly and completely subjected to the uniform treatment now: to be described. The temperature in retort is maintained usually somewhat higher than that employed in retort C, and may range from approximately 1200 degrees to approximately 1300- degrees 6. V The feed of the material through retort J is at such speed that the material is treated therein for a period of approximately 2 hours; During this treatment, the retort is: supplied through gas inlet h With a non-oxidizing gas such as hydrogen or nitrogen, though I may employ carbon dioxide or air in limited quantity, v'whereby only a slight oxidation occurs, or

' I may employ a mixture of'the nonroxidizing gases, hydrogen or nitrogen, or both, with carbon dioxide, or air, or both, being careful that, at most, only a partial oxidation occurs.

The resulting granulated carbon is quite dense, i. e, free from substantial porosity,

has; a glistening surface, and is very uniform in character. The first, treatment described apparently results in-more orlesscrackmg of the volatile hydrocarbons present: inthe raw carbonaceous material treated, with the result, so far as I can best judge, that the carbon set free by such. cracking is deposited in the pores of the residual-y material, thereby materially diminishing itsporosity. second treatmentgives each granule a very characteristics, both very important factors in'the practical use of the material for its intended purposes.

Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent is:

The

uniform heat treatment and uniform surface 1. The process of making granular carbon I mission whi'chconsistsin heatin carbonaceous material over a period of rom 10 to I00 hoursatagradually and slowly increasing temperatuie until it reaches a temperature of not less than, 500 degrees 'centigrade, thereafter continuing the heating at substantially said latter temperature for a Ito 10 hour period, said latter heating operation being conducted in a substantially non-oxidizing atmosphere, and then further heating the materialnot. exceeding 1 100 degrees centigrade for al to 10 hour period at a substantially highertemperature, and in the presence of a substantially non-oxidizing atmosphere.

2. The process of making granularcarbon particularly adapted formicrophonic trans mission which consists in heating carbonaceous material in av non-occidizing' atmos phere, such as hydrogen, for aperiod of between 10 and 100 hours while gradually increasing the temperature thereof until a temperature of not less: than 500? degrees centigrade is attained, maintaining it at: salmstantially said temperature for a period of from 1 to 10 hours, and then further heating the material for a 1 to 10 hour period at a temperature not over 1400' degrees "centigrade in a substantially non-oxidizing atmosphere, such as hydrogen, While sinmltaneously agitating it so as to expose its particles to treatment. 1

In testimony whereof I haveiisi'gnaed the foregoing specification. ELMER. NEWMAN HUNTING. 

